1. Field of the Invention
The present invention relates to a saddle type vehicle having a saddle in which a rider sits astride the saddle, such as a motorcycle, and more particularly, the present invention relates to a vehicle frame structure of the saddle type vehicle.
2. Description of the Related Art
For a saddle type two to four-wheeled vehicle having a saddle in which a rider sits astride the saddle, various types of vehicle frame structures have been proposed and provided so as to enhance running stability and reduce manufacturing costs.
It has been proposed to provide a vehicle frame structure of a motorcycle in which two pairs of swing arms each separately support a front wheel or a rear wheel connected to the vehicle frame, for example, such a structure that a shock absorber unit constituted by a damper and others is disposed below the swing arms. See Japanese Patent No. 3,334,931 (pp. 2-3, FIG. 1).
The vehicle frame of this type has a simple structure and high rigidity. Moreover, since the center of gravity of the motorcycle is located at a lower position in this vehicle frame structure, running stability of the motorcycle is enhanced.
In the field of a saddle type vehicle such as a motorcycle, however, there is always a demand for a more attractive saddle type vehicle which is more competitive in the market.
The above-described vehicle frame structure offers certain advantages in enhancement of running stability of a saddle type vehicle, but development of an improved saddle type vehicle having more enhanced running stability has been demanded.